Lottery tickets represent a special kind of security print which for reasons of security must be protected against see-through and various kinds of forgery.
The lottery tickets hitherto used and sold on the market are protected against see-through by being made from a foil-laminated paper material, usually an aluminum foil laminated to a stiff sheet of paper. The aluminum foil is printed with special printing inks which are volatile and/or require strong solvents. Said inks represent a potential hazard with respect to work environment as well as from a general environmental point of view. Also, the aluminum foil itself is extremely unsuitable from the environmental point of view, both in the manufacture of the foil-laminated sheet of paper itself and in taking care of the waste that is unavoidable in connection with printing and finishing of the product, as well as in destruction of the product after use.
Further, as a result of its sensitivity, the aluminum foil poses production-technical problems in the manufacture of aluminum foil laminated lottery tickets. Heavy demands are made as to printing accuracy, since if the foil is bent, folded or "cracked" during printing, the deformation will remain and the products have to be discarded.
From the forgery point of view, a multilayer product is unsuitable, since it may be delaminated and tampered with, for example by transferring information from one lottery ticket to another. Further, aluminum foil and sheets of paper are available on the market and can be used by forgers with knowledge of printing technique.
In the manufacture of lottery tickets it is of the utmost importance that is should be possible to check the number of lottery tickets made in a simple way. With existing equipment, aluminum foil laminated lottery tickets cannot be machine counted.
It is already known to use different types of coated paper for different applications mostly intended for the manufacture of paper with a bright and uniform quality. These coatings are usually very thin and, further, no suggestions have been made for the manufacture of instant lottery tickets by using a see-through protected base paper coated on both sides.
GB 1 435 686 discloses a security paper which is proof against alteration, especially abrasion of its surface. The paper comprises a paper base layer and an opaque abradable top coating of a contrasting appearance, so that alteration involving abrasion of the top coating can be visually detected. The paper base layer is preferably a dyed paper but neither the grammage nor the degree of transparency of the paper base layer is discussed. The only information about transparency is given in connection with the coating which is stated to be opaque, in the sense that it is opaque under normal conditions of illumination. The specification clarifies in more detail the meaning of opaque by stating that a one pound note is regarded as opaque. It is to be noted that according to the present invention by opaque is meant totally opaque, i.e. a conventional bank note would not be classified as opaque.